Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income (Loss) (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	$ (16,507)
Unrealized gains (losses)	3,861
Amounts reclassified from accumulated other comprehensive income	1,673
Balance at June 30, 2013	(10,973)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	2,244
Unrealized gains (losses)	(106)
Amounts reclassified from accumulated other comprehensive income	(896)
Balance at June 30, 2013	1,242
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	(18,286)
Unrealized gains (losses)
Amounts reclassified from accumulated other comprehensive income	2,371
Balance at June 30, 2013	(15,915)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Balance at December 31, 2012	(465)
Unrealized gains (losses)	3,967
Amounts reclassified from accumulated other comprehensive income	198
Balance at June 30, 2013	$ 3,700